Production of hydrogen cyanide



Patented Jan. 18, 1938 UNITED STATES PATENT OFFlCE 2,105.:231- I rnonuo'rrom or nvnnoor'm OYANIDE Leonid Andrussow, Mannheim, Germany, assignor to I. G. Farbenindustrie Aktiengesellsehatt, Franki'ort-on-the-Main, Germany No Drawing.

Serial No. 1934 5 Claims.

This invention relates to the production of hydrogen cyanide.

It is known to produce hydrocyanic acid by passing a gaseous mixture containing ammonia, hydrocarbons, especially methane, and oxygen at elevated temperature over catalysts, especially those which favour the oxidation of ammonia. For this purpose noble metals, such as platinum metals or gold or silver or alloys of these metals with each other, or also other metallic or oxidic catalysts are proposed.

The catalysts consisting of platinum metals or their alloys with each other, which are especially active, have the drawback that by the action of the reaction gases they gradually undergo a 'marked change in structure whereby their mechanical resistance is impaired.

I have now found that alloys of platinum and iridium containing from a few tenths of one per cent, say one half per cent, to about 15 per cent, preferably from 1 per cent to 10 per cent of iridium can be employed with advantage for the said process, although iridium hasa comparatively high volatility at the high temperatures concerned, by bringing the said alloys into the form of gauze from wires the thickness of which is at least 0.1 millimetre; a thickness of about 0.15 millimetre is very suitable. It is preferable to work at temperatures of from about 950 to 1100 C. Under the said conditions, not only are excellent yields of hydrogen cyanide obtained,

but the catalyst also has a very good stability in spite of the high working temperature and remains active as well as mechanically resistant over several months. This effect is contrary to expectation inasmuch as alloys of platinum and iridium, when exposed to temperatures of the said order, are about four times as volatile as platinum and-about six times as volatile as a corresponding alloy from platinum and rhodium.

The following example will further illustrate the nature of this invention but the invention is not restricted to this example.

Example A gas mixture consisting of 11 per cent of ammonia, 11.5 per cent oi! methane, 15 per cent of oxygen, 2 per cent of hydrogen and the remainder of nitrogen is led at about 1050' C. at a speed 01 500 cubic metres per hour through four nets, arranged closely behind each other having 500 meshes per square centimetre and prepared from wire of a thickness of 0.15 millimetre and preover catalysts the use oi alloys of platinum and Application November 22, 1935, 51,074. In Germany November 29.

pared from an alloy oi platinum and iridium containing 3 per centof iridium. The surface of the nets is 500 square centimetres and they are supported by a few wires of chromium-nickel steel. A good yield of hydrogen cyanide is obtained. The nets are stable for several months. Similar nets of platinum have a smaller stability while nets of platinum-rhodium alloys occupy a mean position.

What I claim is:

1. In the production of hydrocyanic acid by passing a gaseous mixture containing ammonia, hydrocarbons and oxygen at elevated temperatures .over catalysts the use of alloys of platinum and iridium containing from about one-half per cent to about 15 per cent of iridium as catalysts in the form of gauze from wires the thickness of which is at least 0.1 millimetre. I

2. In the production of hydrocyanic acid by passing a gaseous mixture containing ammonia, hydrocarbons and oxygen at elevated temperatures over catalysts the use of alloys of platinum and iridium containing from 1 per cent to 10 per cent of iridium as catalysts in the form oi. gauze from wires the thickness of which is at least 0.1 millimetre.

3. In the production 01 hydrocyanic acid by passing a gaseous mixture containing ammonia, hydrocarbons and oxygen at 950 to 1100 C.

30 iridium containing from about one-half per cent to about 15 per cent of iridium as catalysts in the 7 form of gauze from wires the thickness of which is at least 0.1 millimetre. Y

4. In the production of hydrocyanic acid by passing a gaseous mixture containing ammonia, hydrocarbons and oxygen at 950 to 1100" C. over catalysts the use of alloys of platinum and hid-- ium containing from 1 per cent to 10 per cent of iridium as catalysts in the form of gauze from wires the thickness of which is at least 0.1 millimetre.

5. In the production of hydrocyanic acid by passing a gaseous mixture consisting oi 11 per cent of ammonia, 11.5 per cent of methane, 15 per cent of oxygen, 2 per cent of hydrogen andthe remainder of nitrogen at about 1050 C. over nets having 500 meshes per square centimetre and prepared from wire of a thickness 01' 0.15 millimetre and prepared from an alloy of platinum and iridium containing 3 per cent of irid- 

